Light emission device

ABSTRACT

A light emission device includes: a plurality of semiconductor light-emitting elements; an optical element configured to collimate light emitted from each of the plurality of semiconductor light-emitting elements and output a plurality of collimated beams; a converging portion having a surface of a hyperboloid or a paraboloid configured to converge the plurality of collimated beams; and a wavelength-converting portion including a transmissive region, and a reflective region that surrounds the transmissive region, the transmissive region including a light-incident surface at which the plurality of collimated beams that have been converged by the converging portion enter, wherein the transmissive region includes a phosphor adapted to be excited by the plurality of collimated beams that have been converged by the converging portion.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.17/016,202, filed on Sep. 9, 2020, which claims priority to JapanesePatent Application No. 2019-171453, filed on Sep. 20, 2019. The entirecontents of these applications are hereby incorporated by reference.

BACKGROUND

The present disclosure relates to a light emission device.

A number of light emission devices have been proposed that emit mixedlight that is obtained through mixing of light emitted from asemiconductor light-emitting element and fluorescence emitted from aphosphor. In such a light emission device, for example, blue light thatis emitted from a semiconductor light-emitting element is used to excitea phosphor that emits yellow fluorescence, thereby providing white mixedlight through mixing of the blue light passing through thephosphor-containing portion and the yellow fluorescence emitted from thephosphor (see, for example, International Publication No. 2012/124302).

SUMMARY

When a phosphor is irradiated with light that is emitted from asemiconductor light-emitting element, color unevenness may exist in themixed light resulting through mixing of the light (from thesemiconductor light-emitting element) passing through thephosphor-containing portion and the fluorescence emitted from thephosphor.

In one embodiment, a light emission device according to the presentdisclosure includes: a plurality of semiconductor light-emittingelements; an optical element configured to collimate light emitted fromeach of the plurality of semiconductor light-emitting elements andoutput a plurality of collimated beams; a converging portion having anaspheric surface configured to converge the plurality of collimatedbeams; and a wavelength-converting portion including a transmissiveregion and a reflective region that surrounds the transmissive region,the transmissive region including a light-incident surface at which theplurality of collimated beams enter. The transmissive region includes aphosphor to be excited by the plurality of collimated beams having beenconverged by the converging portion.

According to certain embodiments of the present disclosure, there isprovided a light emission device that suppresses color unevennessexisting in mixed light that is obtained through mixing of light that isemitted from semiconductor light-emitting elements and fluorescence thatis emitted from a phosphor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view schematically showing awavelength-converting portion that includes: a transmissive regionincluding a phosphor; and a reflective region surrounding thetransmissive region.

FIG. 1B is a diagram showing a result of intensity distributioncalculation, on a light-incident surface of the transmissive region, fortwo rows by five columns of collimated beams that have been converged bya spherical lens.

FIG. 1C is a diagram schematically showing a chromatic distribution ofmixed light emitted from a light-outgoing surface of the transmissiveregion.

FIG. 2A is a perspective view schematically showing a light emissiondevice according to an embodiment of the present disclosure.

FIG. 2B is a perspective view schematically showing the inside of thelight emission device depicted in FIG. 2A.

FIG. 3A is a side view schematically showing, as viewed along the Xdirection, how collimated beams emitted from a light source may beconverged by an aspherical lens and be incident on the light-incidentsurface of the transmissive region of the wavelength-converting portion.

FIG. 3B is a side view schematically showing, as viewed along the Ydirection, how collimated beams emitted from the light source may beconverged by the aspherical lens and be incident on the light-incidentsurface of the transmissive region of the wavelength-converting portion.

FIG. 4 is a graph in which lens surfaces according to equation (1) areplotted.

FIG. 5 is a diagram showing a result of intensity distributioncalculation for two rows by five columns of radiated collimated beamsconverged by the aspherical lens, where the aspherical lens is definedby a conic constant k=+0.5.

FIG. 6 is a diagram showing a result of intensity distributioncalculation for two rows by five columns of radiated collimated beamsthat are converged by lenses of various conic constants.

FIG. 7A is a diagram showing the light source in FIG. 2B, in which aframe body and a lid are omitted from illustration.

FIG. 7B is a cross-sectional view taken along the YZ plane,schematically showing how laser light emitted from the semiconductorlight-emitting elements may be reflected by reflective surfaces oflight-reflective members, and collimated by collimating lenses of anoptical element.

FIG. 7C is a cross-sectional view taken along the XZ plane,schematically showing how laser light emitted from the semiconductorlight-emitting elements may be reflected by the reflective surfaces ofthe light-reflective members, and collimated by the collimating lensesof the optical element.

FIG. 8A is a side view schematically showing, as viewed along the Ydirection, how collimated beams emitted from the light source may beconverged by a paraboloid reflector according to a variation and beincident on the light-incident surface of the transmissive region of thewavelength-converting portion.

FIG. 8B is a side view schematically showing, as viewed along the Ydirection, how collimated beams emitted from the light source may beconverged by a paraboloid reflector according to another variation andbe incident on the light-incident surface of the transmissive region ofthe wavelength-converting portion.

FIG. 9 is a diagram schematically showing a spectrum of excitation lightof a single wavelength, and a spectrum of resultant fluorescence.

DETAILED DESCRIPTION Spectrum of Fluorescence

Prior to describing embodiments of the present disclosure, an exemplaryspectrum of fluorescence that is emitted from a phosphor that is excitedby light (excitation light) having a narrow spectral width, e.g., laserlight, will be discussed.

FIG. 9 is a diagram schematically showing a spectrum of excitationlight, and a spectrum of resultant fluorescence. As shown in FIG. 9 ,while the excitation light has a narrow spectral width, the fluorescencehas a broad spectral width. The fluorescence spectrum spans a region oflonger wavelengths than the excitation light wavelength. In practice,when a phosphor is irradiated with excitation light, a portion of theexcitation light will excite the phosphor, while the remainder will betransmitted through the phosphor, reflected by the phosphor, etc., so asto exit the portion containing phosphor without undergoing anywavelength conversion. The resultant light will be light in which theexcitation light having been transmitted through the phosphor and thefluorescence emitted from the phosphor are mixed. For example, when aYAG (Yttrium Aluminum Garnet) phosphor is excited by blue laser lighthaving a wavelength of 455 nm, this phosphor will emit yellowfluorescence. The blue laser light having been transmitted the phosphorand the yellow fluorescence emitted from the phosphor will mix togetherto provide white light. This white mixed light can be utilized in alighting device, for example. Although white may be a representativecolor of mixed light, this is not a limitation; the color of mixed lightcan be adjusted based on the combination of the excitation light and thephosphor.

Findings Serving as the Basis of Embodiments of the Present Disclosure

Next, with reference to FIGS. 1A through 1C, findings serving as thebasis of embodiments of the present disclosure will be described. Aphosphor may be employed in the following manner in a context where thephosphor is irradiated with excitation light, for the purpose ofobtaining mixed light that contains excitation light having beentransmitted through the phosphor and fluorescence emitted from thephosphor.

FIG. 1A is a perspective view schematically showing awavelength-converting portion 40 that includes: a transmissive region 40t including a phosphor; and a reflective region 40 r surrounding thetransmissive region 40 t. The transmissive region 40 t includes alight-incident surface 40 s 1 and a light-outgoing surface 40 s 2, whichare both exposed and are parallel to each other. The transmissive region40 t may be a ceramic in which a phosphor is contained, i.e., a phosphorceramic. Fluorescence that is emitted from the phosphor is substantiallynon-distributed light. Therefore, within the phosphor ceramic, a portionof the fluorescence goes toward the reflective region 40 r and isreflected by the reflective region 40 r. A phosphor ceramic may be madeof a binder of an inorganic material and a phosphor, for example. Thereflective region 40 r may be made of a ceramic, for example. In theexample shown in FIG. 1A, the transmissive region 40 t is made by usinga YAG phosphor and a binder material of aluminum oxide as the mainmaterials, whereas the reflective region 40 r is made of aluminum oxideas the main material. The transmissive region 40 t and the reflectiveregion 40 r exhibit high adhesion with each other, because they bothcontain aluminum oxide.

As an excitation light source for exciting the YAG phosphor contained inthe transmissive region 40 t, for example, a semiconductor laser packagethat emits a plurality of blue collimated beams may be used. Theplurality of collimated beams may be converged with one condenser lens,and the beams having been converged may be used to irradiate thelight-incident surface 40 s 1 of the transmissive region 40 t, wherebymixed light can be obtained. A “collimated beam” refers to a beam thathas been collimated so that its beam diameter remains constant along thetraveling direction of the beam. However, the beam diameter may not bestrictly constant in some cases. Moreover, when a collimated beam isconverged with a condenser lens, its beam diameter will graduallynarrow, and after becoming smallest at the beam waist, again broadengradually. In the present specification, for ease of explanation, theterm “collimated beam” encompasses a collimated beam that has also beentransmitted through a condenser lens.

FIG. 1B is a diagram showing a result of an intensity distributioncalculation, on the light-incident surface 40 s 1 of the transmissiveregion 40 t, for two rows by five columns of radiated collimated beamsthat have been converged by a spherical lens. FIG. 1B illustratesrelative intensities of light in varying degrees of shading, where whitecorresponds to 0% and black corresponds to 100%. In the followingdescription, a mere reference to an “intensity distribution of radiatedcollimated beams” alludes to an intensity distribution of collimatedbeams that are radiated on the transmissive region 40 t and observed atthe light-incident surface 40 s 1. Specific conditions of calculationwill be described later. The region surrounded in a black rectangularframe represents the light-incident surface 40 s 1 of the transmissiveregion 40 t. The light-incident surface 40 s 1 of the transmissiveregion 40 t is located away from the focusing point of any of thecollimated beams that are converged by the spherical lens. As shown inFIG. 1B, mainly the central portion of the light-incident surface 40 s 1of the transmissive region 40 t is irradiated. The plurality ofcollimated beams will become more divergent away from the center. In theexample shown in FIG. 1B, however, the degree of divergence is notlarge, and end portions of the light-incident surface 40 s 1, inparticular the four corners, are barely irradiated. Being excited by thecollimated beams that are incident on the transmissive region 40 t, thephosphor emits fluorescence. Therefore, from the light-outgoing surface40 s 2 of the transmissive region 40 t, white light should ideally beemitted, into which blue light passing through the transmissive region40 t and the yellow fluorescence emitted from the YAG phosphor have beenmixed together. However, in practice, this mixed light may have somecolor unevenness.

FIG. 1C is a diagram schematically showing a chromatic distribution ofmixed light emitted from the light-outgoing surface 40 s 2 of thetransmissive region 40 t. A white region represents a region where whitelight is emitted, whereas a hatched region represents a region wheremore yellowish light is emitted. It can be seen that white light ispredominantly emitted from the central portion of the light-outgoingsurface 40 s 2 of the transmissive region 40 t, while relativelyyellowish light is emitted at the end portions, in particular the fourcorners, thus resulting in substantial color unevenness. A possiblereason for this is as follows. Portions of the fluorescence emitted atlocations that are irradiated with four collimated beams incident at theends of the row direction (the X direction) travel toward the reflectiveregion 40 r, and after being reflected back from the reflective region40 r, exit the light-outgoing surface 40 s 2. At each corner of thereflective region 40 r, fluorescence is reflected from two planes thatare perpendicular to each other. This results in a greater proportion ofyellow light existing than there is blue light, whereby the mixed lightbecomes yellowish at the end portions, in particular the four corners,of the light-outgoing surface 40 s 2 of the transmissive region 40 t.

The inventors have ascribed the reasons for the color unevenness to theintensity distribution of radiated collimated beams at thelight-incident surface of the transmissive region, thereby arriving at anovel light emission device that can reduce color unevenness. This lightemission device includes a converging portion having an aspheric surfacethat converges a plurality of collimated beams that are emitted fromlight sources. The shape of this aspheric surface is appropriatelydesigned so that the intensity distribution of radiated collimated beamshaving been converged thereby will allow color unevenness in the mixedlight to be reduced. Details of the converging portion will be describedlater.

Embodiments

Embodiments of the present disclosure will now be described withreference to the drawings. It should be understood that theimplementations described below are merely embodiments of thetechnological concept of the present invention, and do not limit thepresent invention. Furthermore, in the following description, anyidentical name or identical reference numeral indicates an identical orsimilar element, of which repeated detailed description may be omitted.Note that the size, relative positioning, and the like of any elementthat is depicted in a drawing may be exaggerated for clarity ofexplanation.

In the present specification, when an element is directly disposed on asurface, or when an element is directly disposed on another object thatis directly disposed on the surface, the element is said to have been“disposed on the surface.” In other words, when an element is disposedon or above the surface, such that the element is physically coupledwith the surface, with or without an intermediate object in between, theelement is said to be disposed on the surface. Note that, whenever it isspecifically meant that the element is directly disposed on the surface,the term “directly” will be consistently used. When there is no explicitreference to the element being “directly disposed,” it is meant that themanner of placement may be either direct or indirect.

Example Configuration of Light Emission Device

First, with reference to FIGS. 2A through 2D, an example configurationof a light emission device according to an embodiment of the presentdisclosure will be described.

FIG. 2A is a perspective view schematically showing a light emissiondevice 100 according to an embodiment of the present disclosure. FIG. 2Bis a perspective view schematically showing the inside of the lightemission device 100 depicted in FIG. 2A. In FIG. 2B, an outer shape ofthe housing 50 is indicated by a broken line. For reference, thedrawings illustrate the X direction, the Y direction, and the Zdirection, which are orthogonal to one another.

The light emission device 100 according to the present embodimentincludes: a substrate 10 having a principal face 10 s; a light source 20disposed on the principal face 10 s, the light source 20 beingconfigured to emit two rows by five columns of collimated beams; anaspherical lens 30 having a convex portion 30 c configured to convergecollimated beams; a wavelength-converting portion 40 having atransmissive region 40 t on an optical axis of the aspherical lens 30;and a housing 50 in which the light source 20 and the aspherical lens 30are housed. The row direction is parallel to the X direction, whereasthe column direction is parallel to the Y direction. In the presentspecification, the word “above” or “upward” refers to, relative to wherethe principal face 10 s of the substrate 10 is, the direction in whichthe light source 20 is disposed. The actual orientation of the lightemission device 100 during use may be arbitrarily selected.

The substrate 10 in the present embodiment may have the principal face10 s being parallel to the XY plane, and its thickness may extend alongthe Z direction, for example. The substrate 10 is desirably made of amaterial having a relatively high thermal conductivity in order to allowheat that is emitted from the light source 20 to be quickly released tothe outside. The substrate 10 may have a thermal conductivity of e.g. 20W/mK or more. Examples of main materials for the substrate 10 include,for example: metals, such as Cu, Al, Fe, Ni, and Mo; and ceramics, suchas aluminum nitride and carbon nitride.

The light source 20 in the present embodiment includes: a base part 21;semiconductor light-emitting elements that are disposed in two rows byfive columns on a principal face of the base part 21; a frame body 22being provided on the principal face of the base part 21 and having leadterminals 22 l that, as a whole, surround the semiconductorlight-emitting elements; a lid 23 provided on a frame that is created bythe frame body 22; and an optical element 24 provided on the lid 23. Theoptical element 24 collimates light that is emitted from thesemiconductor light-emitting elements disposed in two rows by fivecolumns within the light source 20, and outputs the two rows by fivecolumns of collimated beams in a direction parallel to the optical axisof the aspherical lens 30 (the Z direction). The traveling directions ofthese collimated beams are generally parallel to one another; however,their traveling directions do not need to be strictly parallel. In thepresent specification, being “parallel” is not limited to being“parallel” in the strictly mathematical sense. In the presentspecification, “parallel” allows for a discrepancy of 1.5 degrees orless from strict parallelism, for example. So long as there are discretecollimated beams, it is possible to irradiate the phosphor-containingtransmissive region 40 t with a plurality of collimated beams. In thecase where the transmissive region 40 t of the wavelength-convertingportion 40 contains a YAG phosphor, the wavelength of blue collimatedbeams may be not less than 420 nm and not more than 480 nm, for example.The wavelength of the collimated beams may be selected in accordancewith the type of phosphor. The sizes of the light source 20 along the Xdirection and along the Y direction may be e.g. not less than 25 mm andnot more than 35 mm, whereas the thickness of the light source 20 alongthe Z direction may be e.g. not less than 10 mm and not more than 15 mm.Details of the light source 20 will be described later.

The aspherical lens 30 in the present embodiment may be a planoconvexlens including a convex portion 30 c and a plate portion 30 f, forexample. The convex portion 30 c and the plate portion 30 f may have arefractive index of e.g. not less than 1.4 and not more than 2.1.Although the convex portion 30 c is shown to be provided at the sidewhere the collimated beams are incident, it may be provided at the sideopposite to the side where the collimated beams are incident. The plateportion 30 f may not even be provided. In the example shown in FIG. 2B,the convex portion 30 c is shown to be thicker than the plate portion 30f, the plate portion 30 f may alternatively be thicker than the convexportion 30 c. A “converging portion having an aspheric surface,” in themeaning of the present disclosure, may be the aspherical lens 30, forexample.

The convex portion 30 c and/or the plate portion 30 f of the asphericallens 30 may be made of at least one of glass, quartz, and sapphire, forexample. The sizes of the aspherical lens 30 along the X direction andalong the Y direction may be e.g. not less than 2 mm and not more than200 mm, and the thickness of the aspherical lens 30 along the Zdirection may be e.g. not less than 2 mm and not more than 150 mm. Theshape of the aspherical lens 30 in upper plan view, i.e., its shape asviewed along the Z direction, may be a circle, for example. Theinterspace between the light source 20 and the aspherical lens 30 alongthe Z direction may be e.g. not less than 1 mm and not more than 300 mm.Details of the aspheric shape of the surface of the convex portion 30 cof the aspherical lens 30 will be described later.

The wavelength-converting portion 40 in the present embodiment has beendescribed with reference to FIG. 1A. Although the light-incident surface40 s 1 of the transmissive region 40 t is shown to have a rectangularshape, it may alternatively have a polygon, a circle, an ellipse, or anysimilar shape thereto.

The transmissive region 40 t of the wavelength-converting portion 40contains a YAG phosphor that is excited by blue light to emit yellowfluorescence; however, this is not a limitation. For example, thetransmissive region 40 t may contain a first phosphor that is excited byblue light to emit yellow or green fluorescence and a second phosphorthat is excited by blue light to emit red fluorescence. By irradiatingthe light-incident surface 40 s 1 of the transmissive region 40 t assuch with blue light, white mixed light can be obtained from thelight-outgoing surface 40 s 2 of the transmissive region 40 t.

Instead of aluminum oxide, the reflective region 40 r of thewavelength-converting portion 40 may be made of zirconium oxide ortitanium oxide as the main material. In order to reduce lighttransmittance, the reflective region 40 r may contain an additive(s)such as yttrium oxide, zirconium oxide, lutetium oxide, and/or lanthanumoxide. In the case where the reflective region 40 r is a ceramic, lightreflectance tends to improve as the reflective region 40 r has a higherporosity. Therefore, within the reflective region 40 r, porosity may beincreased around the transmissive region 40 t than in any portionsoutside thereof. This will allow the fluorescence that is emitted in thetransmissive region 40 t and that heads toward the reflective region 40r to be efficiently reflected by the reflective region 40 r. Thereflective region 40 r may also have the function of allowing the heatthat is emitted in the transmissive region 40 t in response tocollimated beam irradiation to be released outside. This will alleviatedeteriorations of the phosphor in the transmissive region 40 t. The mainmaterial of the reflective region 40 r may be a ceramic or a metal. Thewavelength-converting portion 40 may at least include the transmissiveregion 40 t, and the reflective region 40 r is not needed.

In order to efficiently release heat to the outside, thewavelength-converting portion 40 may further include a heat sink memberon at least one of its upper surface and lower surface. Presence of anon-zero interspace between the wavelength-converting portion 40 and theheat sink member will cause a decrease in the heat-releasing ability;therefore, grease, a dielectric film, or any other member may beprovided in order to fill the interspace between thewavelength-converting portion 40 and the heat sink member.

At the light-incident surface 40 s 1 side of the transmissive region 40t, the wavelength-converting portion 40 may further include a filterthat transmits the collimated beams but that reflects the fluorescencethat is emitted from the phosphor. This can restrain the fluorescencefrom being emitted toward the aspherical lens 30, and thus allow thefluorescence to be efficiently emitted from the light-outgoing surface40 s 2 of the transmissive region 40 t. The filter may be made of amultilayer film of dielectric in which high-refractive index layers andlow-refractive index layers alternate, for example. The multilayer filmof dielectric is able to reflect light in a specific wavelength regionby substantially 100%, while transmitting any other light. Themultilayer film of dielectric may be designed so that this specificwavelength region contains a part or a whole of the wavelength spectrumof the fluorescence.

The sizes of the transmissive region 40 t of the wavelength-convertingportion 40 along the X direction and along the Y direction may be e.g.not less than 0.5 μm and not more than 100 μm, and the thickness of thetransmissive region 40 t along the Z direction may be e.g. not less than0.1 mm and not more than 10 mm. The interspace between the asphericallens 30 and the wavelength-converting portion 40 along the Z directionmay be e.g. not less than 1 mm and not more than 300 mm. In the presentspecification, an “interspace between component parts” is synonymouswith the minimum distance between the component parts.

The housing 50 in the present embodiment may have the shape of acylindrical tube having a circular cross section, for example.Alternatively, the housing 50 may have the shape of a rectangular tubehaving a polygonal cross section, or the shape of a dome. The height ofthe housing 50 along the Z direction is determined by a sum of: thethickness of the light source 20; the interspace between the lightsource 20 and the aspherical lens 30; the thickness of the asphericallens 30; and the interspace between the aspherical lens 30 and thewavelength-converting portion 40. Without being limited to this, therelationship between the height of the housing 50 along the Z directionand dimensions associated with other component parts may be adjusted asappropriate. For example, any other component parts than these may behoused in the housing 50. A reflector, etc., may be disposed to alterthe traveling direction of the collimated beams 20 b at a certain pointalong its path.

Next, FIG. 3A and FIG. 3B will be described. FIG. 3A and FIG. 3B areside views schematically showing how collimated beams 20 b emitted fromthe light source 20 may be converged by the aspherical lens 30 to beincident on the light-incident surface 40 s 1 of the transmissive region40 t of the wavelength-converting portion 40, as viewed along the Xdirection and the Y direction, respectively. In FIG. 3A and FIG. 3B, forease of explanation, the housing 50 is partly illustrated by brokenlines. A lid 50 c of the housing 50 has a throughhole 50 o through whichthe plurality of collimated beams 20 b having been converged by theaspherical lens 30 are allowed to pass, and supports thewavelength-converting portion 40. The wavelength-converting portion 40is supported by an edge 50 e of the throughhole 50 o. A support 50 s,which is a part of the housing 50, protrudes inward from the sidewallportion, and supports the aspherical lens 30. A portion of the plateportion 30 f of the aspherical lens 30 is bonded to the support 50 s.Each region that is interposed between a pair of thin broken linesrepresents the beam width of a collimated beam 20 b. As shown in FIG.3A, the beam width of each collimated beam 20 b is broader along thecolumn direction (the Y direction), and, as shown in FIG. 3B, the beamwidth of each collimated beam 20 b is narrower along the row direction(the X direction). The reason for this will be described later. A blankarrow represents mixed light into which the collimated beams 20 btransmitted through the transmissive region 40 t and the fluorescenceemitted from the phosphor contained in the transmissive region 40 t arecombined.

In the example of FIG. 3A and FIG. 3B, two and five (respectively)collimated beams 20 b are shown to be converged by the aspherical lens30 and incident on the light-incident surface 40 s 1 of the transmissiveregion 40 t. The optical axis of each collimated beam 20 b is partlyvisualized, with a more sparse broken line than the broken linesrepresenting the beam width of the collimated beam 20 b. A focusingpoint F of the aspherical lens 30 corresponds to a point at which theoptical axes of the plurality of collimated beams 20 b would ideallyconverge. However, in practice, the plurality of collimated beams 20 bmay become deviated in position, or the plurality of collimated beams 20b may have non-equal beam diameters; therefore, not necessary allcollimated beams 20 b may actually converge at a single point. Even ifthere is no deviation in position, and the beam diameters are all equal,the diffraction limit of light will not allow all collimated beams 20 bto converge at a point with zero width; therefore, it may be assumedthat not all collimated beams 20 b will converge at a single point asillustrated. Nonetheless, for ease of explanation, the focusing point Fis simply illustrated as a single point in the present specification.

As shown in FIG. 3A and FIG. 3B, the light-incident surface 40 s 1 ofthe transmissive region 40 t is disposed orthogonal to the optical axisof the aspherical lens 30, and is located off the focusing point F ofthe aspherical lens 30. The distance between the light-incident surface40 s 1 of the transmissive region 40 t and the focusing point F may bee.g. not less than 1 mm and not more than 20 mm. So long as thelight-incident surface 40 s 1 of the transmissive region 40 t intersectsthe optical axis of the aspherical lens 30, without a need forreflectors or the like to alter the traveling directions of thecollimated beams 20 b, the light-incident surface 40 s 1 of thetransmissive region 40 t can be irradiated with the plurality ofcollimated beams 20 b having been converged. In the example shown inFIG. 3A and FIG. 3B, the focusing point F of the aspherical lens 30 islocated between the aspherical lens 30 and the light-incident surface 40s 1 of the transmissive region 40 t. All of the plurality of collimatedbeams 20 b diverging from the focusing point F are incident on thelight-incident surface 40 s 1 of the transmissive region 40 t, withoutbeing obstructed by the edge 50 e of the throughhole 50 o. The focusingpoint F may be located within the transmissive region 40 t. In anotherexample, the light-incident surface 40 s 1 of the transmissive region 40t may be located between the aspherical lens 30 and its focusing pointF.

When the light-incident surface 40 s 1 of the transmissive region 40 tis located off the focusing point F of the aspherical lens 30, thelight-incident surface 40 s 1 can be irradiated with defocusedcollimated beams 20 b. This allows the optical density of the collimatedbeams 20 b at the light-incident surface 40 s 1 to be lower than in thecase where the light-incident surface 40 s 1 of the transmissive region40 t is located at the focusing point F of the aspherical lens 30.

Convex Portion 30 c of Aspherical Lens 30

Next, the aspheric shape of the surface of the convex portion 30 c ofthe aspherical lens 30 will be described. The shape of the surface ofthe convex portion 30 c can be defined by its conic constant. Given aconic constant k, and a curvature c=1/R at the lens vertex of theaspherical lens 30 (where R is the radius of curvature), coordinates (X,Y, Z)=(x, y, z) on the lens surface based on an origin that is the lensvertex of the aspherical lens 30 satisfy the following equation (1).

$\begin{matrix}{z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\sum\limits_{i = 2}^{n}{a_{2i}r^{2i}}}}} & (1)\end{matrix}$

In the above equation, z represents a distance between an XY plane thatcontains the lens vertex and the lens surface along the Z direction; andr=(x²+y²)^(1/2) represents a distance between the lens surface and theoptical axis of the aspherical lens 30 on the XY plane. Furthermore,a_(2i)(2i=2, . . . , n) represents the aspheric coefficient.

First, the case where a_(2i)=0 will be described. In this case, equation(1) corresponds to one of the solutions to equation (2).

(1+k)z ²−2Rz+r ²=0  (2)

Equation (2) indicates that, in the case where a_(2i)=0, equation (1)represents one of the following surfaces: a hyperboloid, a paraboloid, asphere, and an ellipsoid.

Next, FIG. 4 will be described. FIG. 4 is a graph in which lens surfacesaccording to equation (1) are plotted, in the case where a_(2i)=0. Asthe conic constant, values from k=−1.5 to k=+1.5 were chosen inincrements of 0.5. Each solid line represents the mathematical functionof equation (1), whereas broken lines represent portions of themathematical function of equation (2) other than equation (1). Therelationship between the conic constant k and the surfaces in the graphis as follows. The surfaces in the graph are: (k<−1) a hyperboloid;(k=−1) a paraboloid; (−1<k<0) an ellipsoid whose minor axis extendsalong the distance r and whose major axis extends along the Z direction;(k=0) a sphere; and (k>0) an ellipsoid whose major axis extends alongthe distance r and whose minor axis extends along the Z direction. Ascan be seen in regions where the distance r is large, the radius ofcurvature of each surface in the graph is: (k<0) greater than the radiusof curvature R; (k=0) equal to the radius of curvature R; and (k>0)smaller than the radius of curvature R. The lens surface of theaspherical lens 30 may correspond to a surface in the graph that isrepresented by one of the solid lines around the origin. Note that theconvex portion 30 c of the aspherical lens 30 in the present embodimentmay have any surface other than that defined by a conic constant k=0.

Next, with reference to FIG. 5 , effects that are obtained with theconvex portion 30 c of the aspherical lens 30 will be described. FIG. 5is a diagram showing a result of intensity distribution calculation fortwo rows by five columns of radiated collimated beams converged by theconvex portion 30 c, where the convex portion 30 c is defined by a conicconstant k=+0.5. The calculation was conducted by using opticalsimulation software, OpticStudio, from Zemax LLC. The conditions ofcalculation were as follows; however, the present disclosure is notlimited to light emission devices designed under the followingconditions of calculation. The spot of each collimated beam 20 b beforebeing incident on the convex portion 30 c has an ellipse shape on the XYplane, with a minor axis along the X direction of 1.0 mm and a majoraxis along the Y direction of 4.9 mm. The spot of each collimated beam20 b was defined with an intensity range that is equal to or greaterthan 1/e² (where e is Napier's constant) times the peak intensity. Theinterval between centers of two adjacent collimated beams 20 b along therow direction (the X direction) is 3.5 mm, and the interval betweencenters of two adjacent collimated beams 20 b along the column direction(the Y direction) is 5.9 mm. The thickness of the aspherical lens 30along the Z direction is 20 mm. The radius of curvature R at the originof the convex portion 30 c is 26.605 mm. The aspherical lens 30 has arefractive index n=1.52308, and there exists a refractive index n=1around the aspherical lens 30. In the case where k=+0.5, the distancefrom the plate portion 30 f of the aspherical lens 30 to the focusingpoint F is 36.2 mm. The distance between the light-incident surface 40 s1 of the transmissive region 40 t and the focusing point F of theaspherical lens 30 is 9.8 mm. The focusing point F is located betweenthe light-incident surface 40 s 1 of the transmissive region 40 t andthe aspherical lens 30.

It can be seen from FIG. 5 that four radiated collimated beams at theends of the row direction (the X direction) have intensity distributionsthat are elongated toward the respective four corners of the rectangularshape of the light-incident surface 40 s 1 of the transmissive region 40t. Thus, the plurality of collimated beams 20 b include at least onepair of outer collimated beams that are radiated toward the corners ofthe light-incident surface 40 s 1, and one or more inner collimatedbeams interposed between the outer collimated beams. The aspherical lens30 exerts less collecting power for the radiated collimated beams 20 bthan does a spherical lens, which would result in an intensitydistribution as shown in FIG. 1B. In other words, the aspherical lens 30is shaped so as to cause the outer collimated beams to be more divergedthan the inner collimated beam(s). As described earlier, there is agreater proportion of fluorescence at the end portions, in particularthe four corners, of the transmissive region 40 t, owing to reflectionat the reflective region 40 r. Allowing the intensity distribution ofradiated collimated beams to become more dispersed at the end portionsof the light-incident surface 40 s 1 of the transmissive region 40 t, inparticular the four corners, introduces greater proportions ofcollimated beams 20 b at such portions than in the case where no suchdispersion is made. As a result of this, the hue of the light emittedfrom the end portions of the light-outgoing surface 40 s 2 of thetransmissive region 40 t, in particular the four corners, can be madecloser to the hue of the light emitted from the central portion of thelight-outgoing surface 40 s 2. This allows for reduction of colorunevenness in the mixed light emitted from the light-outgoing surface 40s 2 of the transmissive region 40 t. The degree of divergence of outercollimated beams may be such that, regarding the beam width along thediverging direction, each outer collimated beam has a beam width that isequal to or greater than 1.1 times the beam width of each innercollimated beam, and preferably 1.3 times the beam width of each innercollimated beam. This allows for a further reduction in colorunevenness. Moreover, since the outer collimated beams decrease inoptical density as they become more diverged, their degree of divergencemay be such that each outer collimated beam has a beam width that isequal to or less than 2.5 times the beam width of each inner collimatedbeam. A beam width along the diverging direction refers to a beam widthalong the major axis of each substantially ellipse-shaped beam, forexample. More preferably, the inner collimated beam to serve as areference for beam width comparison is chosen to be the collimated beamthat is the closest, among the plurality of collimated beams 20 b, tothe center of the aspherical lens when passing through the asphericallens.

Next, with reference to FIG. 6 , the relationship between the conicconstant k of the lens and the intensity distribution of radiatedcollimated beams will be described. FIG. 6 is a diagram showing a resultof intensity distribution calculation for two rows by five columns ofradiated collimated beams that are converged by lenses of various conicconstants. As values of the conic constant, k=−1.5 (hyperboloid), k=−1.0(paraboloid), k=−0.5 (ellipsoid), k=0 (sphere), k=+1.0 (ellipsoid), andk=+1.5 (ellipsoid) were chosen. Relative to the conic constant k=0(sphere), the intensity distribution of radiated collimated beamsbecomes more concentrated at the central portion of the light-incidentsurface 40 s 1 of the transmissive region 40 t as the conic constantvalue decreases while being negative (k<0), and becomes more dispersedat the end portions of the light-incident surface 40 s 1 of thetransmissive region 40 t, in particular the four corners, as the conicconstant increases while being positive (k>0). In the presentdisclosure, the conic constant k of the aspherical lens 30 is chosen inthe range of −15<k<0, or in the range of 0<k<+6.

The above example illustrates that the shape of the surface of theconvex portion 30 c of the aspherical lens 30 is designed by varying theconic constant k. Alternatively, the surface of the convex portion 30 cmay be designed by varying at least one of: the conic constant k, thecurvature c, and the aspheric coefficient a_(2i).

Two representative methods may exist for modulating the intensitydistribution of radiated collimated beams. One method involves using aspherical lens to converge a plurality of collimated beams 20 b that arearranged so that at least one center-to-center distance between themdiffers from any other center-to-center distance. The other methodinvolves using the aspherical lens 30 to converge a plurality ofcollimated beams 20 b that are arranged at a constant pitch as in thepresent disclosure. According to an analysis by the inventors, thelatter allows the light source 20, and hence the aspherical lens 30, tobe smaller in size, whereby the light emission device 100 can becomemore reduced in size.

Alternatively, the light emission device 100 can also be reduced in sizeby configuring the light source 20 so that a plurality of semiconductorlight-emitting elements 25 are mounted within one package. The reason isthat, as compared to the case where the light source 20 is implementedin a plurality of packages and the minimum distance between collimatedbeams 20 b that are emitted from two adjacent packages needs to bereduced, it is easier to reduce the minimum distance between collimatedbeams 20 b that are emitted from two adjacent semiconductorlight-emitting elements 25 within a single package. That is, when theplurality of semiconductor light-emitting elements 25 are mounted withina single package, the range to be irradiated by the plurality ofcollimated beams 20 b can be smaller than in the case where just as manysemiconductor light-emitting elements 25 are divided among a pluralityof packages. This allows the aspherical lens 30 to be smaller in size,and the light emission device 100 to be further reduced in size.

A desirable intensity distribution of radiated collimated beams may bedetermined based on the shape of the light-incident surface 40 s 1 ofthe transmissive region 40 t. Therefore, the aspheric shape of thesurface of the convex portion 30 c of the aspherical lens 30 may beappropriately designed in accordance with the shape of thelight-incident surface 40 s 1 of the transmissive region 40 t. Forexample, in the case where the light-incident surface 40 s 1 of thetransmissive region 40 t has a circle shape, an ellipse shape, or anoval shape, it may be possible to reduce color unevenness in the mixedlight by using an aspherical lens 30 whose convex portion 30 c has anegative conic constant (k<0). An oval shape refers to a shape,resembling a circle or an ellipse, that is constituted by anon-intersecting closed curve and that is axisymmetric with respect toat least one location. The result shown in FIG. 6 indicates, in the casewhere the collimated beams 20 b are disposed in rows and columns, atendency that the four corners of the shape of rows and columnspresented by the collimated beams 20 b are more contracted toward thecentral portion as a negative conic constant (k<0) has a greaterabsolute value. FIG. 6 also indicates a tendency that, as a positiveconic constant (k>0) has a greater absolute value, the four corners ofthe shape of rows and columns presented by the collimated beams 20 b aremore distant from the central portion. When the light-incident surface40 s 1 of the transmissive region 40 t has a circle shape, an ellipseshape, or an oval shape, for example, the surface of the convex portion30 c may have an aspheric shape defined by a surface whose conicconstant is equal to or less than −1.0 (k≤−1.0). When the light-incidentsurface 40 s 1 of the transmissive region 40 t has a rectangular shape,for example, the surface of the convex portion 30 c may have an asphericshape defined by a surface whose conic constant is equal to or greaterthan 0.5 (k≥0.5).

Other than varying the aspheric shape of the surface of the convexportion 30 c of the aspherical lens 30, the intensity distribution ofradiated collimated beams may be modulated by varying the distancebetween the light-incident surface 40 s 1 of the transmissive region 40t and the focusing point F of the aspherical lens 30.

Example Configuration Inside Light Source 20

Next, with reference to FIG. 7A, an example configuration inside thelight source 20 will be described. FIG. 7A is a diagram showing thelight source 20 in FIG. 2B, in which the frame body 22 and the lid 23are omitted from illustration. For ease of explanation, the distancebetween the base part 21 and the optical element 24 is exaggerated.

On the principal face 21 s of the base part 21, the semiconductorlight-emitting elements 25 are disposed in two rows by five columns viasubmounts 26. The emission end faces of the semiconductor light-emittingelements 25 in one row are opposed to the emission end faces of thesemiconductor light-emitting elements 25 in the other row. Thus, theplurality of semiconductor light-emitting elements 25 are arranged inone or more rows and two or more columns or in two or more rows and oneor more columns, along a plane (the XY plane) that is perpendicular tothe optical axis of the aspherical lens 30. Each submount 26 is able toadjust the height of the corresponding semiconductor light-emittingelement 25 along the Z direction. The center-to-center distance betweenadjacent semiconductor light-emitting elements 25 may be e.g. 0.85 mm ormore. This can reduce the mutual influences of heat generated by thesemiconductor light-emitting elements 25. On the other hand, from astandpoint of reducing the size of the light source 20, thecenter-to-center distance between adjacent semiconductor light-emittingelements 25 may preferably be 2.5 mm or less, for example. Although theexample of FIG. 7A illustrates that the plurality of semiconductorlight-emitting elements 25 are disposed at a constant pitch along therow direction, and a constant pitch along the column direction, thesepitches may not be constant. As described above, it is possible tomodulate the intensity distribution of radiated collimated beams byadjusting the center-to-center distance between adjacent semiconductorlight-emitting elements 25. Possible placements of the plurality ofsemiconductor light-emitting elements 25 include a one-row placement anda placement of multiple rows and multiple columns.

On the principal face 21 s of the base part 21, light-reflective members27 are disposed in two rows by five columns. The reflective surface 27r, provided on a slope of each light-reflective member 27, is a surfacethat faces the emission end face of the corresponding semiconductorlight-emitting element 25 and that reflects light emitted from thesemiconductor light-emitting element 25. The angle between thereflective surface 27 r of the light-reflective member 27 and theprincipal face 21 s of the base part 21 is determined by the relativepositioning between the semiconductor light-emitting element 25 and theoptical element 24. Although the example shown in FIG. 7A illustratesthis angle to be 45 degrees, it may alternatively be any angle otherthan 45 degrees. Light that is emitted from the two rows ofsemiconductor light-emitting elements 25 is reflected by the reflectivesurfaces 27 r of the light-reflective members 27 in a direction awayfrom the principal face 21 s of the base part 21, so as to be incidenton the optical element 24. Regarding the two rows of semiconductorlight-emitting elements 25, the semiconductor light-emitting elements 25in one row emit light in the +Y direction, whereas the semiconductorlight-emitting elements 25 in the other row emit light in the −Ydirection. The +Y direction corresponds to the direction of an arrowheadshown in FIG. 7A, whereas the −Y direction corresponds to an oppositedirection to the arrowhead.

The main material of each light-reflective member 27 may be: a glass,such as quartz or BK7 (borosilicate glass); a metal, such as aluminum;or Si, for example. The reflective surface 27 r of each light-reflectivemember 27 is desirably made of a material having a relatively highreflectance with respect to the light emitted by the semiconductorlight-emitting element 25. This material may be a metal or a multilayerfilm of dielectric. The light reflectance of the reflective surface 27 rmay be 70% or more, e.g. 90%, at the peak wavelength of the lightemitted by the semiconductor light-emitting element 25, for example. Thelight-reflective member 27 may include a plurality of light reflectivesurfaces. The light source 20 may include an additional light-reflectivemember(s) other than the light-reflective members 27.

The optical element 24 includes collimating lenses 24 l that arearranged in two rows by five columns. Each collimating lens 24 l isdisposed at a position where light emitted from the correspondingsemiconductor light-emitting element 25 passes through that collimatinglens 241. The optical element 24 allows two rows by five columns ofcollimated beams to be emitted from the collimating lenses 24 l arrangedin two rows by five columns.

The collimating lenses 24 l of the optical element 24 may be made of atleast one of glass, quartz, sapphire, a transparent ceramic, and aplastic, for example. The sizes of the optical element 24 along the Xdirection and along the Y direction may be e.g. not less than 15 mm andnot more than 20 mm, and the thickness of the optical element 24 alongthe Z direction may be e.g. not less than 2.0 mm and not more than 5.0mm.

Note that the number and relative positioning of semiconductorlight-emitting elements 25 are not limited to the number and relativepositioning illustrated in FIG. 7A. There may be multiple semiconductorlight-emitting elements 25. In order to allow for reducing the size ofthe light source 20, the number of semiconductor light-emitting elements25 may be 30 or less, for example. The same is also true of thecollimating lenses 24 l in the optical element 24, and of thelight-reflective members 27.

Each semiconductor light-emitting element 25 may be a laser diode, forexample. The laser diode emits coherent light. The laser diode has astructure in which an n-side cladding layer, an active layer, and ap-side cladding layer are disposed in this order. The laser diodefurther includes an electrode (n-side electrode) located at the n-sidecladding layer side, and an electrode (p-side electrode) located at thep-side cladding layer side. The electrodes may be made of alight-transmissive and electrically-conductive material, so as to beutilized as cladding layers. By applying voltage to the n-side electrodeand the p-side electrode and causing a current equal to or greater thana threshold value to flow, laser light is emitted from the laser diode.In FIG. 7A, the laser light is emitted from an end face of eachsemiconductor light-emitting element 25 in a direction parallel to the Ydirection. A spot created by the emitted laser light has a far fieldpattern of an ellipse shape whose major axis extends along the Zdirection and whose minor axis extends along the X direction. The laserdiode is able to emit laser light in any of the colors belonging in thevisible region, for example. In the case where light outside of thevisible region is to be utilized as a portion of the mixed light, thelaser diodes may emit laser light other than that of the visible region,e.g., ultraviolet. Among the plurality of semiconductor light-emittingelements 25 shown in FIG. 7A, all may emit laser light of the samewavelength, or at least one may emit laser light of a differentwavelength. In order to reduce color unevenness, it is preferable thatlight from all of the plurality of semiconductor light-emitting elements25 is in the same color.

In the case where a YAG phosphor is used as the phosphor, laser diodesthat emit blue laser light may be used, for example. The emission peakwavelength of blue light is desirably in a range of not less than 420 nmand not more than 480 nm, and more desirably in a range from 440 nm to460 nm. Examples of laser diodes that emit blue laser light includesemiconductor laser devices containing a nitride semiconductor. Asnitride semiconductors, GaN, InGaN, and AlGaN can be used, for example.A semiconductor laser device containing a nitride semiconductor is ableto emit light ranging from ultraviolet to the visible region by varyingits composition.

As necessary, the semiconductor light-emitting element 25 may behermetically sealed within a package. The base part 21, the frame body22, and the lid 23 correspond to a package within which thesemiconductor light-emitting elements 25 are hermetically sealed. Giventhat the semiconductor light-emitting elements 25 are laser diodes, thelight source 20 can be referred to as a semiconductor laser package. Inthe case where the semiconductor light-emitting elements 25 are laserdiodes that emit laser light of a relatively short wavelength (e.g. awavelength of about 480 nm or less), if the emission end faces of thelaser diodes are exposed to the atmospheric air, the ends faces may besubject to deterioration during operation, owing to dust collectioneffects and the like. Such an end face deterioration may result in adecrease in the optical output power of the laser diodes. In order toenhance reliability of the laser diodes and extend their life time, thelaser diodes are desirably hermetically sealed.

Note that the semiconductor light-emitting elements 25 may includelight-emitting diodes (LED), which emit incoherent light. Preferably,the semiconductor light-emitting elements 25 are laser diodes, becauselaser light will result in small losses of light when used incombination with a lens.

Similarly to the substrate 10 of the light emission device 100, the basepart 21 is desirably made of a material having a relatively high thermalconductivity, in order to allow the heat emitted from the plurality ofsemiconductor light-emitting elements 25 to be quickly released to theoutside. Similarly, the submounts 26 are desirably made of a materialhaving a high thermal conductivity. Examples of the main material of thebase part 21 include metals, such as Cu, and ceramics, such as aluminumnitride and carbon nitride. Examples of the main material of thesubmounts 26 include aluminum nitride, carbon nitride, and the like.

Each semiconductor light-emitting element 25 is bonded at is lowersurface to an upper surface of the submount 26. Therefore, in the casewhere a side surface of the semiconductor light-emitting element 25 isthe light-outgoing surface, the semiconductor light-emitting element 25emits light in a direction parallel to the principal face 21 s of thebase part 21. For example, via an electrically conductive layer such asAu—Sn, each semiconductor light-emitting element 25 may be fixed to thesubmount 26 having a metal film provided thereon. Note that thesemiconductor light-emitting element 25 may be provided so as todirectly emit light along the Z direction, in which case thelight-reflective member 27 is not needed. In regions of the submount 26other than where the semiconductor light-emitting element 25 isprovided, an electrically conductive layer for wire connection may beprovided in order to facilitate electrical connection between theplurality of semiconductor light-emitting elements 25 and the leadterminals 22 l of the frame body 22 via wires.

Next, with reference to FIG. 7B and FIG. 7C, the differing beam widthsof the collimated beams 20 b shown in FIG. 3A and FIG. 3B will bedescribed. Herein, the semiconductor light-emitting elements 25 includelaser diodes. FIG. 7B and FIG. 7C are cross-sectional views takenrespectively along the YZ plane and along the XZ plane, schematicallyshowing how laser light emitted from the semiconductor light-emittingelements 25 may be reflected by the reflective surfaces 27 r of thelight-reflective members 27, and collimated by the collimating lenses 24l of the optical element 24. The lid 23 includes a light-transmittingmember 23 t that closes an opening 23 o, and spacers 23 s that create aninterspace between the light-transmitting member 23 t and the opticalelement 24. As described above, the laser light that is emitted fromeach semiconductor light-emitting element 25 is divergent widely alongthe Z direction, but not very much along the X direction. Therefore, asshown in FIG. 7B, when laser light that is divergent widely along the Zdirection is reflected upward and then collimated, the collimated beam20 b will have a broad beam width along the Y direction. On the otherhand, as shown in FIG. 7C, when laser light that is not very divergentalong the X direction is reflected upward and then collimated, thecollimated beam 20 b will not have a very broad beam width along the Xdirection. Therefore, a spot created by the collimated beam 20 b emittedfrom the optical element 24 along the Z direction has an ellipse shapewhose major axis extends along the Y direction and whose minor axisalong the X direction in the XY plane. The far field pattern of laserlight that is emitted from each semiconductor light-emitting element 25is not limited to the shape described herein; however, the major axisand the minor axis may be reversed, for example.

Variations of Converging Portion Having an Aspheric Surface

Next, with reference to FIG. 8A and FIG. 8B, variations of theconverging portion having an aspheric surface according to the presentdisclosure will be described. FIG. 8A and FIG. 8B are side viewsschematically showing, as viewed along the Y direction, how collimatedbeams 20 b emitted from the light source 20 may be converged by aparaboloid reflector 31 according to each variation and be incident onthe light-incident surface 40 s 1 of the transmissive region 40 t of thewavelength-converting portion 40. In FIG. 8A and FIG. 8B, the substrate10 and the housing 50 are omitted from illustration. The paraboloidreflector 31 according to each variation has a reflective surface 31 mof a paraboloid shape. The reflective surface 31 m reflects light thattravels in parallel to an axis 31 a of the paraboloid (the Z direction),so as to be converged onto a focusing point F on the axis 31 a. Not allportions of the reflective surface 31 m shown in FIG. 8A and FIG. 8B arerequired; it suffices if the portions to be struck by the light exist.The shape of any portion other than the reflective surface 31 m of theparaboloid reflector 31 is not limited. In the examples shown in FIG. 8Aand FIG. 8B, the light source 20 emits collimated beams 20 b arranged intwo rows by five columns along the Z direction. Among the fivecollimated beams 20 b reflected by the reflective surface 31 m of theparaboloid reflector 31, it is the middle beam that the light-incidentsurface 40 s 1 of the transmissive region 40 t is perpendicular to theoptical axis of.

In the example shown in FIG. 8A, the middle beam is reflected by thereflective surface 31 m along the X direction. Mixed light, which isrepresented by a blank arrow, is emitted from the light-outgoing surface40 s 2 of the transmissive region 40 t along the X direction. In theexample shown in FIG. 8B, the light source 20 is more distant from theaxis 31 a than in the example shown in FIG. 8A. In the example shown inFIG. 8B, too, all of the collimated beams 20 b emitted from the lightsource 20 are converged onto the focusing point F. The middle beam isreflected in an obliquely upward direction by the reflective surface 31m. The mixed light is emitted in an obliquely upward direction from thelight-outgoing surface 40 s 2 of the wavelength-converting portion 40.If the light source 20 were located closer to the axis 31 a than in theexample of FIG. 8A, the mixed light would be emitted in an obliquelydownward direction from the light-outgoing surface 40 s 2 of thewavelength-converting portion 40.

In the examples shown in FIG. 8A and FIG. 8B, the focusing point F islocated between the paraboloid reflector 31 and the light-incidentsurface 40 s 1 of the transmissive region 40 t; alternatively, thelight-incident surface 40 s 1 of the transmissive region 40 t may belocated between the paraboloid reflector 31 and the focusing point F.The focusing point F may be located inside the transmissive region 40 t.

The reflective surface 31 m according to each of these variations doesnot need to have a paraboloid shape, but may have the shape of anaspheric surface such as a hyperboloid or an ellipsoid, depending on theintended use. Color unevenness in the mixed light can be reduced alsowhen the converging portion having an aspheric surface according to thepresent disclosure is an aspheric surface reflector such as theparaboloid reflector 31.

Light emission devices according to embodiments of the presentdisclosure are applicable to various light sources, e.g., a lightingdevice, a headlight for vehicles such as an automobile, a light sourceof a projector, a light source for an endoscope, and so on.

What is claimed is:
 1. A light emission device comprising: a pluralityof semiconductor light-emitting elements; an optical element configuredto collimate light emitted from each of the plurality of semiconductorlight-emitting elements and output a plurality of collimated beams; aconverging portion having a surface of a hyperboloid or a paraboloidconfigured to converge the plurality of collimated beams; and awavelength-converting portion comprising a transmissive region, and areflective region that surrounds the transmissive region, thetransmissive region including a light-incident surface at which theplurality of collimated beams that have been converged by the convergingportion enter, wherein the transmissive region includes a phosphoradapted to be excited by the plurality of collimated beams that havebeen converged by the converging portion.
 2. The light emission deviceof claim 1, wherein the light-incident surface of the transmissiveregion intersects an optical axis of the converging portion, and islocated off a focusing point of the converging portion.
 3. The lightemission device of claim 1, wherein the plurality of collimated beamsoutput from the optical element are parallel to one another.
 4. Thelight emission device of claim 1, wherein the plurality of semiconductorlight-emitting elements are arranged in one or more rows and two or morecolumns or in two or more rows and one or more columns along a planethat is perpendicular to an optical axis of the converging portion. 5.The light emission device of claim 4, wherein a surface shape of theconverging portion is adapted to a shape of the light-incident surfaceof the transmissive region.
 6. The light emission device of claim 1,wherein the light-incident surface of the transmissive region has arectangular shape.
 7. The light emission device of claim 1, wherein, theconverging portion is an aspherical lens; and the aspherical lens has aconic constant k such that −15≤k−1.0.
 8. The light emission device ofclaim 7, wherein a focusing point of the aspherical lens is locatedbetween the aspherical lens and the light-incident surface of thetransmissive region.
 9. The light emission device of claim 8, whereinthe aspherical lens has a conic constant k such that −1.5≤k≤−1.0. 10.The light emission device of claim 1, further comprising: a housing inwhich the plurality of semiconductor light-emitting elements, theoptical element, and the converging portion are housed, wherein thehousing comprises a lid configured to support the wavelength-convertingportion, the lid having a throughhole through which the plurality ofcollimated beams that have been converged by the converging portion areallowed to pass.
 11. The light emission device of claim 10, wherein thewavelength-converting portion is supported by an edge of the throughholeof the lid.
 12. The light emission device of claim 10, wherein thehousing comprises a sidewall portion and a support that protrudes inwardfrom the sidewall portion and supports the converging portion.
 13. Thelight emission device of claim 1, wherein the light-emitting elementsare laser diodes.
 14. The light emission device of claim 13, furthercomprising a package in which the plurality of laser diodes arehermetically sealed.
 15. The light emission device of claim 1, whereinthe reflective region is made of a ceramic.
 16. The light emissiondevice of claim 15, wherein the reflective region is made of aluminumoxide as a main material.